Differential developmental rates and demographics in Red Kangaroo (Osphranter rufus) populations separated by the dingo barrier fence

We show that one population of red kangaroos outside the dingo barrier fence has fewer females and joeys, and also grows up faster than a neighboring population that is protected by the fence. We argue that the impacts of contrasting predation pressures across the fence, for kangaroos and other prey, need further investigation. Decommissioning the dingo barrier fence has been suggested to reduce destructive dingo control and encourage a free transfer of biota between environments in Australia. Yet the potential impacts that over a century of predator exclusion might have had on the population dynamics and developmental biology of prey populations has not been assessed. We here combine demographic data and both linear and geometric morphometrics to assess differences in populations among 166 red kangaroos (Osphranter rufus)-a primary prey species of the dingo-from two isolated populations on either side of the fence. We also quantified the differences in aboveground vegetation biomass for the last 10 years on either side of the fence. We found that the age structure and growth patterns, but not cranial shape, differed between the two kangaroo populations. In the population living with a higher density of dingoes, there were relatively fewer females and juveniles. These individuals were larger for a given age, despite what seems to be lower vegetation biomass. However, how much of this biomass represented kangaroo forage is uncertain and requires further on-site assessments. We also identified unexpected differences in the ontogenetic trajectories in relative pes length between the sexes for the whole sample, possibly associated with male competition or differential weight-bearing mechanics. We discuss potential mechanisms behind our findings and suggest that the impacts of contrasting predation pressures across the fence, for red kangaroos and other species, merit further investigation.

Automated summary

Our study reveals that the red kangaroo population outside the dingo barrier fence has fewer females and joeys and grows faster compared to the population protected by the fence. Further investigation is needed to understand the effects of different predation pressures on kangaroos and other prey. Decommissioning the dingo barrier fence in Australia has been suggested to promote the free movement of biota but its potential impacts on prey populations have not been assessed.